The Basic Knowledge of Acrylic Machining

With the fast development of CNC machining China, CNC acrylic this process is not mysterious in prototype manufacturing industry in China or the whole world. Acrylic is also known as Polymeric Methyl Methacrylate (PMMA). Its chemical name is polymethyl methacrylate, which has good transparency, chemical stability and weather resistance, easy dyeing, easy processing and beautiful appearance. It has the reputation of crystal plastic. It is widely used in instrumentation parts, automobile lights, optical lenses, transparent pipes, etc.

photo courtesy of Wayken Rapid Manufacturing

Acrylic properties

PMMA Sheet is made by PMMA which also called as organic glass or arcylic, it is a transparent organic glass sheet with light transmittance above 92%. PMMA sheet has even color, non-water stain and precision thickness tolerance; it also has better weather ability, especially widely used in ourdoor. The surface hardness and gloss is excellent, it can be made into all kinds of products in different shapes with high transparent characteristic.

Before we understand the processing of acrylic machining products, we need to briefly understand the relevant properties of acrylic materials. The following sheet are some basic technical datas of acrylic sheet:

1.1 Advantages:

1) Unparalleled outdoor weather resistance, the perspex sheet is coated with high-concentration UV absorber, and the metal base is sprayed with imported automotive paint to ensure long-term weather resistance, no fading, and the using life is about 5-8 years.

2) The transparent plate is crystal clear and transparent, 200 times than the glass product.

3) The surface is high in gloss, smooth and flat, with excellent light transmission, soft light and dazzling.

4) Green environmental protection and waste materials can be completely recycled, and recycling is simple and easy. The light transmission performance is good, the light source product is reduced correspondingly, thus it can save power and the use cost is reduced.

5) Excellent surface hardness and scratch resistance, the product has good protection for the built-in light source and prolongs the service life of the light source.

6) Good chemical resistance, better than most other plastic materials.

1.2 Disadvantage

perspex sheet is relatively low in hardness, so the heat resistance will be poor, and then the elongation will be relatively low, which will lead to easy chipping and deformation, etc., and the color is not stable enough, it is easy to fluff during use.

Post-treatment of CNC acrylic products

Although the original acrylic material is transparent, in many cases it does not meet the actual needs of use. Acrylic machining parts that do not have any post-treatment surface will look a little foggy, not completely transparent, as shown below.

Actually, most parts would be required post-processing during acrylic machining, which is generally divided into two kinds: one requires polishing and is fully transparent. In order to achieve the effect of total transparent clear, this requires a very sophisticated post-processing technology, because it is a purely manual operation, and the requirements for polishing workers are also very high. The effects of different workers sanding and polishing the same workpiece may also be quite different. It is also the core reason why quality differences occur.

In order to achieve a completely transparent effect, it is generally divided into two steps: the first step, manual sanding, sanding is carried out step by step, from rough to finishing, generally starting from 80# sandpaper, up to 2000#, to remove the part surface machining amrks. The type of sandpaper selected will vary depending on the requirements of the parts. In the second step, after sanding the surface of the part, it need to be processed with polishing wax to achieve a completely transparent clear effect.

Due to the manual operation, the above two-step operation will consume a large amount of work time. Sometimes a automotive lamp with complicated surface and details may take more than one working day to complete.

photo courtesy of Wayken Rapid Manufacturing

The second type is sand blasting. In some specific applications, the surface is required to have a rough “sanding effect”, which is generally required for texture. If it is required to be very foggy, generally spray glass sand, if the requirements are higher, you can use white corundum to achieve it.

photo courtesy of Wayken Rapid Manufacturing

3. Acrylic VS PC transparent parts

Many people may know that in the processing of making clear transparent prototyping parts, except for using acrylic materials, PC material is also an option. The difference between the two are as follows:

PC raw materials are generally resistant to high temperatures, around 120-150 °C. If customers demand high-temperature transparent materials, then PC is the best choice. Acrylic’s advantage, the most important thing is high transparency. After polishing, the transparency can achieve the full clear effect, which is unmatched by PC materials. Although the PC is transparent, the effect is not as good as acrylic. Acrylic has another kind of calling by organic glass in the industry. It is known that glass is very brittle, so the physical properties of acrylic are also brittle. The defect of poor tolerance causes acrylic to break down accidentally. It needs to be prevented during processing.

In summary, whether acrylic machining products can be exquisitely meet customer requirements depends mainly on three points: First, materials, materials determine the machinability and transparency from the beginning, and different levels of material selection according to different industry applications and customer requirements. Sometimes, imported materials will be used. Second, machining processing, whether it is milling or lathe processing, the machining process determines the dimensional accuracy of the product when processing the product shape. The third is manual processing, which is a decisive step in the completion of a transparent part. It is also a factor in assessing the perfection of a factory to make acrylic crafts. The truly skilled and experienced factory presents its customers with products that are perfect without any flaws.

WayKen has professional polished team with more than 5 years polishing experiences. Besides the transparent parts, we are striving for improving the process of plastic prototyping of our customers. We treat each product as a craft. All of our customers have witnessed the quality of our transparent acrylic machining products. They all greatly appreciate our work. Especially in the field of transparent processing of lamp lights, WayKen has the most extensive experience and advanced technology in the industry, providing superior quality and service for some world-class car brands. If you have any relevant questions or needs, please feel free to contact us.

Author: EyeT Solutions

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